In plants for the production and/or rolling of strip materials such as paper or metal products, rolls known as "with a rotating shell" comprising a deformable tubular jacket have been used for some time.
It is known that a rolling mill generally comprises two working rolls supported respectively by at least two back-up rolls, the assembly being mounted in a stationary stand. For a variety of reasons and, in particular, in order to control the flatness of the rolled product, arrangements are provided for modifying the profile of the working rolls or of the back-up rolls. For this purpose, use is made of bending devices which act on the ends of the shafts of the rolls or, alternatively, on the profile of the external surface of the roll, a combination of both arrangements being furthermore possible. To act on the external profile of the roll, particularly in the case of back-up rolls, use is advantageously made of rolls comprising a deformable tubular jacket rotating freely around its axis on a shaft consisting of a strong beam resting on the two uprights of the stand and defining the axis of rotation. Between the stationary shaft and the tubular jacket, and over the entire length of a generatrix of the jacket, there is placed a series of shoes with fluid bearings having outwardly a cylindrical supporting face whose curvature is equal to that of the internal surface of the jacket, and each actuated by one or more jacks whose chambers are arranged within the beam or which are integrally fastened to the shoes. Oil is injected under pressure between the supporting face of the shoe and the internal surface of the jacket so as to form a film enabling the jacket to rotate owing to a hydrostatic or hydrodynamic effect, it being possible, furthermore, for both these principles to be combined. A feed system enables the thrusts of each shoe to be adjusted individually so as to control the profile of the deformable jacket, for example as a function of measurements of flatness which are performed at different points across the width of the rolled product.
At least one of the back-up rolls or, alternatively, in some cases, of the working rolls, may be equipped in this manner. A roll with a rotating shell of this type is described, for example, in applicant's French Pat. No. 83 16341.
In an arrangement of this kind, each shoe for supporting the jacket forms an inverted fluid bearing in which the shoe is stationary relative to the shell, which rotates around the shaft, and this gives rise to a number of problems of implementation on an industrial scale which are particularly due to the fct that the genetrix line of the fluid bearings is long in relation to their diameter.
As already indicated, the fluid bearings may be of a hydrostatic or hydrodynamic type.
In the most common case, where the bearings are of the hydrostatic type, each shoe comprises, on its face facing the jacket, a chamber which is fed with fluid under pressure at a certain leakage rate, enabling the lubricating film to be formed. The latter needs to be recovered in order to be cooled and reinjected into the bearings. In the case where hydrodynamic shoes are employed, the circulation of fluid in the form of a thin layer produces a heating effect and, in order to prevent the temperature from rising gradually to an excessive value, the fluid must also be recovered in order to be cooled before being reinjected into the roll.
Until now, this recovery of the lubricating fluid was carried out merely by gravity, but it was found that this recovery was difficult to implement, especially when the speed of rotation of the shell became considerable.